Abstract

Being able to select relevant visual information from among irrelevantinformation is critical for the successful accomplishment of many day to dayactivities. However, the locus of attentional selection is not always under thecontrol of the observer. Certain events and stimuli in the visual environment havebeen shown to control selection against observers’ intentions and goals. These aresaid to capture attention in an automatic and stimulus driven manner. The eventsand stimuli that capture attention can be static (colour, shape, size, etc.) ordynamic (motion, flicker, etc.).This thesis examines the effect of dynamic stimuli on attentional selectionby using a visual search paradigm. The findings suggest that neither motion per senor the onset of motion captures attention. They also suggest that when lowrefresh rate motion is used, capture occurs, but this effect cannot be attributed tocapture by motion onset (Chapter 3). Further, the second study suggests thatattention capture is observed using low refresh rate motion onsets because theyare not masked as compared with the static items in the display. Thus capture isput down to a relatively better visual quality and stimulus encoding rather thanmotion (Chapter 4). The findings from this thesis also suggests that when backand forth oscillatory motion is used, capture re-emerges, but this effect is bestattributed to a change in direction that happens to be temporally unique (Chapter5). Another important finding is that in attention capture by abrupt onset, only oneonset is prioritised in search (Chapter 6). The findings overall argue for a strongrole of low level factors in attention capture by dynamic stimuli.